Scientists uncover a previously unknown mechanism of memory formation

It takes a lot to make a memory. New proteins have to be synthesised, neuron structures altered. While some of these memory-building mechanisms are known, many are not. Some recent studies have indicated that a unique group of molecules called microRNAs, known to control production of proteins in cells, may play a far more important role in memory formation than previously thought.

Now, a new study by scientists on the Florida campus of The Scripps Research Institute has for the first time confirmed a critical role for microRNAs in the development of memory in the part of the brain called the amygdala, which is involved in emotional memory. The new study found that a specific microRNA - miR-182 - was deeply involved in memory formation within this brain structure.

''No one had looked at the role of microRNAs in amygdala memory,'' said Courtney Miller, a TSRI assistant professor who led the study. ''And it looks as though miR-182 may be promoting local protein synthesis, helping to support the synapse-specificity of memories.''

In the new study, published in the Journal of Neuroscience, the scientists measured the levels of all known microRNAs following an animal model of learning.

A microarray analysis, which enables rapid genetic testing on a large scale, showed that more than half of all known microRNAs are expressed in the amygdala. Seven of those microRNAs increased and 32 decreased when learning occurred.

The study found that, of the microRNAs expressed in the brain, miR-182 had one of the lowest levels and these decreased further with learning. Despite these very low levels, its overexpression prevented the formation of memory and led to a decrease in proteins that regulate neuronal plasticity (neurons' ability to adapt) through changes in structure.